The effect of growth at elevated concentrations of CO2 on
stomatal density and stomatal index (the fraction of epidermal
cells that are stomata) is one of the most intensively studied
environmental controls on stomatal development. CO2 enrichment
changes the stomatal density of different species and different
accessions (ecotypes) of Arabidopsis thaliana (Fig. 3b and primary ref).
With stomatal densities ranging from 45 to 720mm^2 the mean
response is an 11% reduction in density with a doubling of the CO2
concentration (Fig. 3b), and which is insensitive to the basal stomatal density.